New user
Anyone that wishes to use the 400 MHz spectrometers, must follow the training protocol. Training begins with some reading and videos to introduce the NMR spectrometer, basic NMR methodology and safety instruction. Thorough reading of the usage rules for the spectrometers is also required. Automated operation of the Neo 400 is straightforward and requires a single training session wit the NMR Director, while use of the 400 MR requires more extensive training and passing a test of your ability to correctly and safely operate the instrument. Practical experience with the 400 MR should initially occur within a research group, with trainees accompanying senior group members to the spectrometer and observing, and then graduating to running spectra with the senior member observing the trainee. If additional individual training is required, this can be arranged with the NMR TA or Director. When the trainee feels competent the "practical" can be scheduled with the NMR TA.
Checklist for new NMR users
o Watch the Intro to NMR presentation (U. of Alberta).
o Read the Magnet Safety Document.
o Watch the quench video.
o Print and fill out the authorization form, and submit it with your advisor's signature to the NMR director.
Neo 400
o Read the policies for the the Neo 400.
o Contact the NMR Director to set up a time for training to run experiments using IconNMR Automation
o If you need to run VT experiments or operate the spectrometer manually contact the NMR director for additional training.
400 MR
o Read the policies for the 400 MR.
o Read the Spectrometer Basics document.
o Accompany senior group members and watch them use the spectrometers.
o Accompany senior group members and have them watch you while you run spectra.
*Additional individual training is available from either the NMR TA or the NMR Director.
o When you feel comfortable acquiring contact the NMR Director to have your account created.
o Arrange with the NMR TA to take your practical quiz on the spectrometer.
o Take the form and your Brandeis ID card to the Chemistry Office (you will be given key access).
Here is a brief "Intro to NMR" presentation from the University of Alberta. It provides a nice introduction to some of the components of the NMR spectrometer (magnet, probe, console) as well as a brief description of why NMR is useful.
Magnet Safety
Use of the Brandeis NMR Facility spectrometers is a privilege and not a right. All users must work cautiously around the high-field magnets. Failure to do so can result in costly instrument damage and serious personal injuries, including death. Each user must understand the hazards present and follow all safety procedures.
Strong Magnetic Fields
The NMR magnet needs no external power source nor can it be readily or easily turned off. Be aware that:
The magnet is ALWAYS ON!
Magnetic field strengths of 9.4 Tesla to 18.8 Tesla can be found within the Brandeis NMR Facility. NMR magnets have strong, static magnetic fields. Their strengths are usually described in terms of Gauss or Tesla units. (1 T = 10,000 G)
Earth’s magnetic field ~.05 mT (.5 G)
Refrigerator magnet .01 T (100 G)
Electromagnet (e.g. junkyard) 1.5 T (15,000 G)
Clinical MRIs 1.5 – 3 T (15,000-30,000 G)
Superconducting NMRs
400 MHz 9.4 T (94,000 G)
500 MHz 11.7 T (117,000 G)
600 MHz 14.1 T (141,000 G)
800 MHz 18.8 T (188,000 G)
There are large attractive forces associated with these magnets and in fact, every magnet has a stray magnetic field that extends out past the physical structure of the magnet. These attractive forces will be exerted on equipment and people brought into proximity of the magnet. The closer to the magnet one goes the larger the attractive force. The larger the mass of the equipment, the larger the attractive force.
The location where the magnetic field strength drops to 5 Gauss is indicated by chains and colored lines on the floor around each magnet. The magnetic field inside the 5 G region can cause damage to medical implants and pacemakers. DO NOT ENTER THE 5 G REGION WITHOUT APPROVAL OF YOUR PHYSICIAN IF YOU HAVE ANY MEDICAL IMPLANTS.
All magnetic objects should be kept outside the 5 G line. This includes keys, wallets, pocket knives, tools, etc. Assume any piece of metal is magnetic until proven otherwise.
Metal objects can be attracted to the magnet causing flying metal projectiles. Ferromagnetic objects can reach a speed approaching 40 mph entering the bore of the magnet. These objects can cause personal injury or death if there is anyone between them and the center of the magnet. If an object strikes the magnet, it can distort the magnet’s wires, internal dewars, or become lodged inside the magnet bore. Any of these can cause the magnet to quench (see Oxygen Displacement). Even small metal objects such as staples or paper clips can cause problems (if they get stuck to the magnet) by distorting the magnetic field and interfering with shimming.
While not a safety issue, the stray fields inside the 5 G can wipe out magnetic information stored on ATM and credit cards. Mechanical watches may be permanently damaged by these stray fields.
Gas cylinders and other equipment should only be moved in the area near the NMR magnets by authorized personnel (i.e. the NMR staff and other specially trained personnel).
Always remember that even though your body cannot feel the strength of the magnetic field, you must always remember its presence. An analogy from Jim Frye (Varian Instruments) describes this perfectly:
“You are walking on the rim of the Grand Canyon in a very heavy fog at night. You know the abyss is on your right, but you can’t see quite where it is. How careful would you be?”
Cryogens
The liquid helium and liquid nitrogen present in the NMR magnets and the portable dewars can pose several dangers including asphyxiation and frostbite. Only trained personnel should transport the dewars or attempt to fill the NMR magnets.
Temperature of liquid helium = -269 degrees C (-451 degrees F)
Temperature of liquid nitrogen = -196 degrees C (-385 degrees F)
Oxygen Displacement
Superconducting NMR magnets contain a large solenoid or coil made up of several kilometers of superconducting wire. This coil is in a bath of liquid helium (up to 260 L for some NMR magnets within the Department). The wire contains and passes electric current without resistance only when cryogenically cooled to 4 K by liquid helium; the current contained in the coil produces the magnetic field. If the solenoid or cryogenic system fails, the wire becomes resistive and generates heat as the electric current stored in the solenoid is lost; a situation referred to as a magnet quench. During a magnet quench, there will be a sudden, large, rapid, and noisy expulsion of helium gas from the magnet as liquid helium vaporizes into a gas (1L of liquid helium expands to ~750L of gas). Magnet quenches are very rare events but if a quench occurs:
• There will be a sudden and loud release of helium gas from the top of the magnet. Clouds of water vapor will appear as the air around the magnet cools. Frost will appear on top of the magnet.
• The rapidly expanding gas emanating from the magnet can displace the air in the room and there is a possibility of asphyxiation in a confined space.
(picture of a controlled quench at the University of Alberta)
In case of a quench you should:
· Leave the room immediately
· Tell anyone in the vicinity to evacuate
· Warn others not to enter the room
· Notify NMR personnel immediately
Each magnet room is equipped with an oxygen sensor which will produce audible andvisual alarms if the level of oxygen in the air drops to potentially dangerous levels (possibly as a result of a quench).
Here is a video provided by Bruker Biospin, Inc. There is an animation demonstrating what happens within the magnet to cause a quench, followed by video footage of an actual quench in the Bruker facility.
